In general, a compressor is a mechanical apparatus for compressing a refrigerant or other various operation gases and raising a pressure thereof, by receiving power from a power generation apparatus such as an electric motor or turbine. The compressor has been widely used for an electric home appliance such as a refrigerator and an air conditioner, or in the whole industry.
The compressors are roughly classified into a reciprocating compressor in which a compression space for sucking or discharging an operation gas is formed between a piston and a cylinder, and the piston is linearly reciprocated inside the cylinder, for compressing a refrigerant, a rotary compressor in which a compression space for sucking or discharging an operation gas is formed between an eccentrically-rotated roller and a cylinder, and the roller is eccentrically rotated along the inner wall of the cylinder, for compressing a refrigerant, and a scroll compressor in which a compression space for sucking or discharging an operation gas is formed between an orbiting scroll and a fixed scroll, and the orbiting scroll is rotated along the fixed scroll, for compressing a refrigerant.
Recently, a linear compressor has been developed among the reciprocating compressors. In the linear compressor, a piston is coupled directly to a linearly-reciprocated driving motor to prevent a mechanical loss by motion conversion, improve the compression efficiency and simplify the configuration.
FIG. 1 is a view illustrating a conventional power supply apparatus applied to a reciprocating compressor. A DC power supply unit V for rectifying a household or industrial alternating current power (not shown) into a direct current is provided, and a control unit (not shown) controls inverter switches S1-S4 in pulse width modulation (PWM) type to supply an alternating current Vm to a linear motor. The DC power supply unit V has a rectifying section for rectifying an AC power and a DC link section, which is a typical construction, so that illustration and description thereof are omitted. The DC power passed through the rectifying section (not shown) and the DC link section (not shown) is changed into an AC power (Vm) having an appropriate amplitude and frequency by the ON/OFF operation of the inverter switches S1-S4, and this AC power (Vm) is applied to the linear motor (precisely, a coil of the linear motor).
Since such a conventional power supply apparatus should employ four inverter switches in order to apply an AC power to the linear motor, the on/off control of the four inverter switches and the circuit configuration are considerably complicated, and the inverter switches have a different reaction time. Hence, there is a probability that a desired AC power may not be applied to the linear motor. In addition, there is a problem that manufacturing costs rises by the application of a plurality of inverter switches.